Pirolli and Card are using foraging theories from ecology and anthropology to understand how people find information in data-rich environments such as the internet. They believe web surfers rely on prehistoric instincts to maximise their yield when they hunt and gather morsels of information.

Foraging theory relies on the concept that animals will make choices that maximise their "benefit per unit cost". A rabbit might have a high energy value, but it costs a lot to catch - a rat might be much easier prey. Learning when to move on from a location that's been 'overgrazed' is another challenge for foragers. Pirolli and Card believe information foragers face the same problems which can be solved in the same way.

Pirolli and Card have developed an artificial forager to test whether the theory produces useful results. They set their model to work looking for target documents in a database containing more than a million documents and found that the forager took the fastest route. They then recruited eight human volunteers and asked them to perform the same task. Again, their routes closely matched the ideal one.

Such research could help database and Web designers to create more productive information resources. The theory could prove particularly useful at that crucial moment when a forager starts thinking about leaving one patch in search of another. Another idea that has developed is the idea of 'information scent' to keep people 'on track'.

But the costs and benefits of foraging for information aren't so easy to measure. Another problem is that foraging models tend to assume environments stay the same over time, whereas information ecologies are nothing if not dynamic. Ingenious 'informavores' - and those who seek to provide them with information - can actively manipulate their environment.

And even if information foraging theory works, there's no guarantee that it will be used to benefit the forager. Think of insectivorous flowers that lure flies with the scent of carrion. As Card points out: "The vendor's interests may not correspond with the searcher's. They may camouflage information to hide it or mimic something that they think you want. Banner ads, especially ones with fake buttons on them, are an example." So next time you're hunting down information on the Web, beware. It could smell like a juicy rabbit, but turn out to be a rat!